Zero indexed...

src/imports/utils.py

@@ -304,7 +304,7 @@ class Book:
                         except asyncio.TimeoutError:
                             await m.edit(content='Message Timed out.')
                         else:
-                            self._current_page = int(msg.content)
+                            self._current_page = int(msg.content) - 1
                     elif str(reaction.emoji) == self._bot.book_emojis['unlock']:
                         self._locked = False
                         await self._message.remove_reaction(reaction, self._channel.guild.me)